Red flag: How do scientists know the universe is expanding?

The fact that the universe is expanding at an accelerating rate is probably known to everyone in the modern world and has even spawned jokes. LIFE decided to find out exactly what signs astronomers use to determine this is the case in the universe.

An effect called redshift is observed in the universe. This is an amazing physical phenomenon. As a light source moves away from the observer, the light waves it emits appear longer than they actually are. The longest wavelength is that of red light. The shortest are purple and blue, respectively. And the farther away a shiny object is from us, the redder it appears to our eyes.

Edwin Hubble saw in the 1920s that the universe was filled with millions of galaxies and immediately noticed a striking feature. That is, galaxies that are more distant will necessarily be redder. The deeper you go, the more red it becomes. Therefore, the most distant objects can no longer be seen with the naked eye, but only through special infrared telescopes that detect such long-wave radiation. For this reason, the James Webb Space Observatory was converted to infrared light to allow it to see as far into the depths of space as possible.

So it turns out that galaxies aren’t just flying apart, they’re flying away faster and faster. This simply surprised cosmologists. They believed that the energy of the Big Bang should weaken over time and that gravitational reaction should slow the retreat of galaxies. It was even believed that the universe would one day actually collapse and return to a singularity. Well, it turns out that everything is much more complicated.

Modern science is already able to compare the relative positions and movements of galaxies with respect to each other, and is discovering that galaxies are grouped into “collections” called clusters. For example, our Milky Way galaxy belongs to the Local Group of galaxies, which also includes the neighboring Andromeda galaxy M 33 (in the constellation Triangulum) and his 100 other galaxies

.These clusters are also arranged in a specific way rather than in a random order. They form superclusters and eventually whole “threads” of incredible size, so-called filaments. This created an image of a fantastical web, a network-like, large-scale structure of the universe.

Nothing expands within the filament (e.g. within a cluster or supercluster). All of these clusters maintain their integrity normally and never fall apart. Moreover, scientists have made it perfectly clear that Andromeda, for example, is currently moving in our direction. Or are we (the Milky Way) moving towards it, it depends, it’s all relative. In 4 billion years, two galaxies will collide.

The expansion of the universe occurs between the threads of these giant galactic superclusters. There is a gap between them. An explanation was needed – what was there? What would happen there? And the only answer that astrophysicists and cosmologists have now reached is that it is not gravity that is at work, but the opposite force, antigravity. And it not only moves the threads of the universal web away from each other, but also stretches and expands the space between them. Let’s assume that we understand, thanks to Albert Einstein, that gravity is a “curvature” of space, and that everything tends to bend like a funnel toward the center of this curvature.